Existing RF communications networks comprise large numbers of individual broadband RF systems. Typically, the RF systems share a common RF band for reception and a common RF band for transmission that is different from the receiving RF band, thereby providing for simultaneous reception and transmission. Accordingly, in forming a secure communications link between the individual RF systems, it is necessary to provide distinct transmission and reception paths. Further, it is desirable that each individual RF system be able to communicate with any other RF system in the network.
When metallic conductors are used to link a plurality of RF systems, the connecting cable must be shielded from electromagnetic and electrostatic radiation. Also, using metallic conductors results in transmitted data not being secure against unauthorized detection by common and well known means. In addition, faults in metallic transmission cable may result in arcing thus causing a fire hazard. Further, electrical isolation and impedance matching are required. Where two or more metallic cables are in proximity to each other, adjacent cables are susceptible to electromagnetic cross-talk and interference. All of these problems are avoided by optical fiber transmissions.
The use of fiber optic transmission links in all forms of communication systems is rapidly expanding because fiber optic systems have tremendous advantages over metallic conductor links. Besides being smaller and lighter than metallic conductor systems, fiber optic systems offer complete electrical isolation, extremely high-speed wideband capability, low signal attenuation, and complete immunity to both noise and broadband spectrum interference. The use of RF signal devices with fiber optic cable requires the conversion of the RF signal to one that can be transmitted over an optical fiber path. Since signals from multiple broadband RF systems require separate optical paths, the connecting fiber optic cable is large and bulky in a communications network supporting large numbers of individual broadband RF systems.